A number of arpeggio systems have been described heretofore. Examples are the Kniepkamp U.S. Pat. No. 3,842,184; Deutsch U.S. Pat. No. 3,854,366; and Adams U.S. Pat. No. 3,954,038. In all of these systems the input intelligence representing operated keys of a keyboard is presented to the arpeggio system in parallel form. The parallel registration is scanned rapidly until an operated key is identified, then the scanner is halted while the required note is sounded by selecting a corresponding keyer from a parallel array of 36 or more keyers, and after the desired note duration time has expired scanning is resumed. The large number of connections required in such systems is a severe limitation when it is desired to implement the circuits in LSI form.
Organs have been described which economize on hardware and wiring complexity by using multiplexed keyboards to control multi-pitch note generators over a single time division multiplexed signal buss. The arpeggio system described herein is specifically intended for use in such systems. A co-pending patent application entitled "Electronic Organ With Multiple Pitch Note Generators", Ser. No. 610,773, now U.S. Pat. No. 4,038,896 filed Sept. 5, 1975, describes an electronic organ with a modified keyboard and special interface circuitry arranged to multiplex signals generated by operation of playing keys on a single buss to facilitate implementation of note generators in LSI form. The circuitry of this multiplexed keyboard is repeated in the present disclosure. Alternative forms of multiplexed keyboards are shown in the Deutsch U.S. Pat. No. 3,696,661 and in Kmetz U.S. Pat. No. 3,875,842.